This research program will identify factors which modify rates of protein synthesis and protein degradation in the lung. Experiments will be carried out using rat lungs perfused in situ by newly-developed techniques. Effects of hormonal, metabolic and other factors will be defined using perfused lungs and localized to specific steps in the pathway of turnover. These steps include supply of amino acids and high-energy phosphates, and reactions of peptide-chain initiation and elongation in the ribosome cycle. Additional experiments will extend these studies to include synthesis of specific proteins important to normal function: proteins associated with the surface active fraction and collagen. Understanding of factors modifying turnover of whole lung protein and of specific proteins required for physiological function will contribute to a better understanding of the biochemistry of the normal lung and, thus, of the mechanisms underlying pulmonary disease.